This filter allows you to import metadata from YAML and markdown files selectively, using SQL-like queries. The source can be any metadata field in a markdown or YAML file. The field's list of values can be filtered using a condition (e.g., date >= 2010), sorted by different properties, and grouped.

Using just pandoc and this filter, one can create complex documents, including static websites, from data in YAML "databases." (See yst for an earlier dedicated tool that did this.)

Example of input:

---
papers:
  select: articles
  from: articles.yaml
  where: 'year > 2009'
  group: author
  order: author, title asc
...

This filter only looks for select fields in the top-level of the metadata hierachy.

To run it,

pandoc --lua-filter select-meta.lua sample.md